On the nature and evolution of the human mind

Alzheimer's Disease and Its Possible Evolutionary Origin: Hypothesis

The enormous, 2-3-million-year evolutionary expansion of hominin neocortices to the current enormity enabled humans to take over the planet. However, there appears to have been a glitch, and it occurred without a compensatory expansion of the entorhinal cortical (EC) gateway to the hippocampal memory-encoding system needed to manage the processing of the increasing volume of neocortical data converging on it. The resulting age-dependent connectopathic glitch was unnoticed by the early short-lived populations. It has now surfaced as Alzheimer's disease (AD) in today's long-lived populations. With advancing age, processing of the converging neocortical data by the neurons of the relatively small lateral entorhinal cortex (LEC) inflicts persistent strain and high energy costs on these cells. This may result in their hyper-release of harmless Aβ_1-42 monomers into the interstitial fluid, where they seed the formation of toxic amyloid-β oligomers (AβOs) that initiate AD. At the core of connectopathic AD are the postsynaptic cellular prion protein (PrPC). Electrostatic binding of the negatively charged AβOs to the positively charged N-terminus of PrPC induces hyperphosphorylation of tau that destroys synapses. The spread of these accumulating AβOs from ground zero is supported by Aβ's own production mediated by target cells' Ca2+-sensing receptors (CaSRs). These data suggest that an early administration of a strongly positively charged, AβOs-interacting peptide or protein, plus an inhibitor of CaSR, might be an effective AD-arresting therapeutic combination.

COVID-19: Lockdown and its impact on medical students: A cross sectional study from a medical school in Mauritius

Background

The objectives of the study were to identify the psychological impacts of lockdown on medical students due to COVID-19 and to discover the educational perplexities being faced by these students during the lockdown.

Methods

A cross-sectional study was conducted at Sir Seewoosagur Ramgoolam Medical College (SSRMC), Mauritius. Questions were designed after an extensive review of the literature, so as to ensure relevance to meet the objectives of the study.

Results

Out of 700 undergraduate medical students, 663 participated, which equates to a response rate of 95%. 348 (52.5 %) of the students were stationed in their hometown and the remaining 315 (47.5 %) were stationed in Mauritius. 464(70%) of the students suffered from the psychological impacts of lockdown whereas 634(95.6%) of students suffered from the educational impact thereof. Mauritian students suffered a greater educational impact aOR4.236[1.606-11.173]. Psychological impacts aOR 1.280 [0.917-1.789] and educational impacts aOR 2.464 [1.076-5.647] were more prevalent in hometown-based students. Students pursuing their clinical studies had aOR1.219 [ 0.531-2.798] a greater educational impact as compared to preclinical studies.

Conclusion

Lockdown triggered both educational and psychological impacts on medical students. On a psychological basis it was proven that the lockdown induced a feeling of guilt and had a greater psychological impact in pre-clinical students. The COVID-19 situation was simultaneously indicated to be a motivator in the majority of students; however, juxtaposed to this was the fact that various students felt as if they couldn't study at the same level that they were accustomed to due to the uncertainty of the situation.

Integrated phylogeny of the human brain and pathobiology of Alzheimer's disease: A unifying hypothesis

The disproportionate evolutionary expansion of the human cerebral cortex with reinforcement of cholinergic innervations warranted a major rise in the functional and metabolic load of the conserved basal forebrain (BF) cholinergic system. Given that acetylcholine (ACh) regulates properties of the microtubule-associated protein (MAP) tau and promotes non-amyloidogenic processing of amyloid precursor protein (APP), growing neocortex predicts higher demands for ACh, while the emerging role of BF cholinergic projections in Aβ clearance infers greater exposure of source neurons and their innervation fields to amyloid pathology. The higher exposure of evolutionary most recent cortical areas to the amyloid pathology of Alzheimer's disease (AD) with synaptic impairments and atrophy, therefore, might involve attenuated homeostatic effects of BF cholinergic projections, in addition to fall-outs of inherent processes of expanding association areas. This unifying model, thus, views amyloid pathology and loss of cholinergic cells as a quid pro quo of the allometric evolution of the human brain, which in combination with increase in life expectancy overwhelm the fine homeostatic balance and trigger the disease process.